Linear response to spin-dependent and spin-independentfields of alkali metal clusters

Abstract

We have obtained the dipole response functions of alkali-metalclusters to spin-dependent and spin-independent fields within theframework of the time-dependent local-spin-densityapproximation. As test cases we have studied the response ofspherical jellium clusters with spin-saturated configurations(Na9+, Na8 and Na20) and withfully spin-polarized configurations (the spherical isomer of Na6+ and Na13). For a spin-dependent excitationwe have obtained in all these clusters a strongly collective spinmode of surface type lying at lower energies than the unperturbedparticle-hole excitations. This mode uncouples cleanly from theelectric dipole mode (Mie plasmon) in the case of spin-saturatedclusters, but if the ground state breaks spin symmetry by a finitespin polarization the two modes turn out to be intertwined in theresponses to spin-dependent as well as spin-independent fields.